Diffractive backlight display and system
A diffractive backlight system includes a light source and a plate light guide. A surface of the plate light guide is configured with a diffraction grating that couples light out of the plate light guide and concentrates the light into a localized region of space. The diffractive backlight system may be used with at least one light valve array to form a display that generates images for viewing in the localized region of space. The display may be incorporated in head-mounted displays in order to generate focused augmented or virtual reality images for wearers.
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This application is a continuation patent application of and claims the benefit of priority to International Application No. PCT/US2016/040904, filed Jul. 2, 2016, which claims the benefit of priority to U.S. Provisional Patent Application Ser. No. 62/214,976, filed Sep. 5, 2015; and also to International (PCT) Application No. PCT/US2016/40582, filed Jun. 30, 2016, the entire contents of which are herein incorporated by reference.
BACKGROUNDIn recent years, head-mounted display (“HMD”) technology has increased in popularity with applications in virtual and augmented reality. An HMD is a display device worn on a user's head typically in the form of eyeglasses, goggles, a helmet, or a visor. The display device may be a single small electronic display unit positioned in the field of view of one eye of the user when the HMD is worn by the user, or the display device may be implemented with two separate small electronic display units positioned in the field of views of both eyes of the user when the HMD is worn by the user. For example, the small electronic display units may be implemented using either a small plasma display panel or a liquid crystal display. A small display unit used in an HMD may also be implemented with one or more lenses, collimating reflectors, and semi-transparent mirrors that focus the image created with the display panel. An HMD may use one display unit to create an augmented reality viewing experience, or an HMD may be implemented with two display units to create a virtual reality viewing experience.
Various features of examples and embodiments in accordance with the principles described herein may be more readily understood with reference to the following detailed description taken in conjunction with the accompanying drawings, where like reference numerals designate like structural elements, and in which:
Certain examples and embodiments may have other features that are one of in addition to and in lieu of the features illustrated in the above-referenced figures. These and other features are described below with reference to the above-referenced figures.
DETAILED DESCRIPTIONEmbodiments in accordance with the principles described herein provide diffraction grating-based backlight displays implemented with a diffractive backlight system. The diffractive backlight system comprises a light source and a plate light guide. A surface of the plate light guide is configured with a diffraction grating. According to some embodiments, the diffraction grating may comprise curved diffractive features (e.g., curved ridges and grooves). Light generated by a light source may be coupled into the plate light guide along a plate-light-guide edge. The diffraction grating is configured to couple light out of the plate light guide and to concentrate the light in a localized region of space located a distance from the diffraction grating. For example, the diffraction grating may couple out a portion of the light that is coupled into the plate light guide. A first light valve array, such as a liquid crystal display, may be disposed in the path of the light output from the diffraction grating to form a display that concentrates images for viewing in the localized region of space. In some embodiments, the display may include a second light valve array disposed in the path of light passing through the first light valve array in order to provide eye accommodation in the localized region of space. In an embodiment, the second light valve array may be a planar light valve array. In another embodiment, the second light valve array may be a pixelated contact lens worn by a viewer. One or two of the diffraction grating-based backlight displays may be used in head-mounted displays in order to generate focused augmented or virtual reality images for wearers.
In some embodiments, the curved diffractive features may follow or be defined by a hyperbolic curve (i.e., defined by or based on a hyperbola) and thus may be “hyperbolic-shaped.” In particular, the curved diffractive features may be concentric hyperbolic-shaped curved diffractive features (e.g., concentric hyperbolic-shaped alternating curved ridges and grooves), according to some embodiments. In other embodiments, the curved diffractive features or the curved ridges and grooves that form the diffraction grating 102 may be either semicircular or concentric semicircular in shape (e.g., semicircular with the common center 110 of curvature located away from the edge 108). In yet other embodiments, another curved shape that is substantially neither hyperbolic-shape or semicircular shape may be employed to define a curve of the curved diffractive features.
In the example of
The plate light guide 100 may be a plate optical waveguide in the form of an extended, substantially planar sheet or slab of optically transparent, dielectric material. The plate light guide 100 may comprise any one of a number of different optically transparent materials or comprise any of a variety of dielectric materials including, but not limited to, one or more of various types of glass, such as silica glass, alkali-aluminosilicate glass, borosilicate glass, and substantially optically transparent plastics or polymers, such as poly(methyl methacrylate) or acrylic glass, and polycarbonate. In some embodiments, the plate light guide 100 may include a cladding layer on at least a portion of a surface of the plate light guide 100 (not illustrated) to facilitate total internal reflection.
The diffraction grating 102 may be formed using any one of many different microfabrication techniques, including, but not limited to, wet etching, ion milling, photolithography, anisotropic etching, and plasma etching. For example, as shown in
The pattern and feature spacing of the diffraction grating 102 causes first order diffracted light to be diffractively coupled out of the plate light guide 100 and converge in a substantially localized region of space called an “eyebox.”
eyebox width=f×σ
In
It should also be noted that the coupled out of the diffraction grating 102 is effectively confined to the light-transmission region 404 and the eyebox 406. As a result, when the viewer's eye 502 is located outside the eyebox 406, or outside the light-transmission region 404, light output from the diffraction grating 102 does not enter the viewer's eye 502 and the diffraction grating 102 appears black.
The diffractive backlight system 300 may be combined with a light valve array to form a display that projects images onto the retina of a viewer's eye when the viewer's eye is located in the eyebox 406.
In other embodiments, a plate light guide may comprise a plurality of diffraction grating segments that corresponds to different region of the diffraction grating 102 and are separated by unpatterned spaces. The diffraction grating segments of the plurality may be two-dimensional diffraction grating segments, for example. Although the diffraction grating segments correspond to different regions of the diffraction grating 102 and are separated by unpatterned spaces, the diffraction grating segments collectively couple out light and concentrate the light in the same manner as the diffraction grating 102.
It should be noted that plate light guides formed from diffraction grating segments that correspond to different regions of the diffraction grating 102 are not limited to rectangular-shaped diffraction grating segments as shown in
A plate light guide configured with diffraction grating segments that correspond to different regions of the diffraction grating 102 concentrate light into localized region of space in the same manner as the plate light guide 100 described above with reference to
Any one of the displays described above may be included in a head-mounted display (“HMD”) to show virtual or augmented reality images.
It is appreciated that the description of the disclosed embodiments herein is provided to enable any person skilled in the art to make or use the present disclosure. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the disclosure. Thus, the present disclosure is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.
Claims
1. A display comprising:
- a plate light guide having a diffraction grating at a surface of the plate light guide, the diffraction grating having curved diffractive features configured to diffractively couple light out of the plate light guide and to concentrate light coupled out of the plate light guide into an eyebox; and
- a first light valve array oriented substantially parallel to the plate light guide and positioned so that the light coupled out of the plate light guide passes through the first light valve array to form an image in the eyebox.
2. The display of claim 1, wherein the curved diffractive features comprise alternating concentric curved ridges and grooves that share a common center located a distance from an edge of the plate light guide.
3. The display of claim 1, wherein the curved diffractive features have a hyperbolic-shaped curve.
4. The display of claim 3, wherein the curved diffractive features comprise concentric hyperbolic-shaped curved diffractive features.
5. The display of claim 1, further comprising a light source configured to provide light, the provided light being coupled into the plate light guide along an edge.
6. The display of claim 1, wherein a feature spacing of the curved diffractive features decreases with increasing distance from an edge of the plate light guide along which light is coupled into the plate light guide.
7. The display of claim 1, wherein the diffraction grating causes light trapped within the plate light guide to diffract and couple first order diffracted light out of the plate light guide and concentrate the first order diffracted light in the eyebox.
8. The display of claim 1, further comprising a second light valve array oriented substantially parallel to the plate light guide and positioned so that light that emerges from the first light valve array passes through the second light valve array.
9. The display of claim 1, further comprising a pixelated contact lens configured to be worn on a viewer's eye, wherein the pixelated contact lens comprises a plurality of individually operated pixels that control an amount of light that enters the viewer's eye when the viewer's eye is located in the eyebox.
10. The display of claim 1, wherein the diffraction grating comprises a plurality of two-dimensional diffraction grating segments configured to concentrate the light coupled out of the plate light guide into the eyebox.
11. A method to display an image, the method comprising:
- coupling light into a plate light guide, the light being generated by a light source;
- diffractively coupling out a portion of the light from the plate light guide through a diffraction grating at a surface of the plate light guide, the diffraction grating concentrating the diffractively coupled-out light portion into an eyebox; and
- modulating the diffractively coupled-out light portion using a first light valve array oriented substantially parallel to the plate light guide to form viewable images within the eyebox.
12. The method of claim 11, wherein the diffraction grating comprise curved diffractive features having a feature spacing that decreases with increasing distance from an edge of the plate light guide along which the light is coupled into the plate light guide.
13. A head-mounted display comprising:
- a plate light guide having a diffraction grating configured to diffractively couple out a portion of light input to the plate light guide and concentrate light coupled out of the plate light guide into an eyebox;
- a first light valve array oriented substantially parallel to the plate light guide and positioned so that the light coupled out of the plate light guide passes through the first light valve array; and
- a display control connected to the first light valve array, the display control operating the first light valve array to form an image in the eyebox.
14. The head-mounted display of claim 13, wherein the diffraction grating comprise curved diffractive features at a surface of the plate light guide.
15. The head-mounted display of claim 14, wherein the curved diffractive features are concentric hyperbolic-shaped curved diffractive features.
16. The head-mounted display of claim 14, wherein the curved diffractive features comprise alternating curved ridges and grooves that share a common center located a distance from an edge of the plate light guide along which the light is input to the plate light guide.
17. The head-mounted display of claim 13, wherein the diffraction grating comprises curved diffractive features having a feature spacing that decreases with increasing distance from an edge of the plate light guide along which light is coupled into the plate light guide from a light source.
18. The head-mounted display of claim 13, wherein the diffraction grating is configured to cause light trapped within the plate light guide to diffract and couple first order diffracted light out of the plate light guide and to concentrate the first order diffracted light in the eyebox.
19. The head-mounted display of claim 13 further comprising a second light valve array oriented substantially parallel to the plate light guide and positioned so that light that emerges from the first light valve array passes through the second light valve array.
20. The head-mounted display of claim 13 further comprising a pixelated contact lens configured to be worn on a viewer's eye, wherein the pixelated contact lens comprises a plurality of individually operated pixels that control an amount of light that enters the viewer's eye when the viewer's eye is located in the eyebox.
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Type: Grant
Filed: Feb 25, 2018
Date of Patent: Jun 30, 2020
Patent Publication Number: 20180180793
Assignee: LEIA INC. (Menlo Park, CA)
Inventor: David A. Fattal (Mountain View, CA)
Primary Examiner: Alan B Cariasco
Application Number: 15/904,406
International Classification: G02B 27/01 (20060101); F21V 8/00 (20060101); G02C 7/04 (20060101); G02B 5/18 (20060101);